This invention relates to the planting of trees adjacent to pavements and structures which are subject to damage by a growing root system of the trees. It is a recognized phenomanon that the root systems of trees seek out and reach for moisture and nutrients from the surrounding soil, and that in many trees there are runner-roots that tend to follow closely beneath the grade level so as to penetrate directly under paving such as sidewalks and the like, and under foundations of building structures. Damage is likely as the runner-roots grow and volumetrically displace pavements and structures, lifting them upwardly. Therefore, it is a general object of this invention to provide a planter box that can be assembled around a tree to control the growth pattern of the root system, and/or any such growth or shrubbery planted closely adjacent to pavements and structures that require protection against displacement thereby.
It is prior art practice to grow young trees in ferrous containers several times deeper than the diameter of the container. These planters have been provided with removable bottoms, and have simply been placed in the ground with backfill therearound, whereupon the tree quickly takes root and the container soon rusts away. In practice, rusting away of the container requires two or three years, prior to which the root system has been effectively established and directed so as to emanate from beneath the open bottom of the container. It is an object of this invention to provide this root control effect in an improved planter box assembled of panels, in which the tree may be grown from seed, or alternately into which the tree may be installed or transplanted at the time of final planting. With the present invention, the planter box is of a depth that accomodates the root system of an immature tree, and extends from ground level to a substantial depth approximating the depth of state of the art nursery containers, some of which are several feet deep.
State of the art planter boxes of the type under consideration are not altogether satisfactory, it being an object of this invention to improve upon the planter boxes that have been employed for root control. With the present invention, construction of the planter box is structurally degradable, both mechanically and materially, so as to yield to growth of the tree root system and disintegrate as and when the tree matures.
Heretofore, planter boxes for this purpose have been of square plan form, with no thought applied to the natural radial growth pattern of the root systems, and with no thought applied to the state of the art digging of a hole for planting such trees. In practice, powered augers dig a round hole which is compatable with the radial growth of a root system. However, a square box does not fit a round hole, and it becomes necessary to manually dig out corners of the round hole in order to receive the square box. This extra manual labor is eliminated with the present invention which provides a planter box of polygonal plan form which is substantially round.
Heretofore, planter boxes for root control have been made of permanent form with non-degradable and permanent material which does not disintigrate with time and having smooth impervious walls, with no thought applied to its restriction of future root system growth as the tree matures. Consequently, said permanent state of the art planter boxes for root control remain integral in the ground without yielding to root growth, in order to direct the root system downwardly. However, this unyielding character of prior art planter boxes adversely restricts and chokes the root system as and when the tree matures and increases in caliper. Therefore, it is an object of the invention to provide a planter box that will burst apart and disintegrate in due time by yielding to the growth of the root system and the inevitable increased caliper of the tree. With the present invention, the planter box is fragmented and is structurally demolished as and when the root system and tree caliper exceeds the restrictive limits of the planter box, whereupon the pieces thereof remain buried or erupt as fragments and debris. With the present invention a Homo-Plastic material is used for this planter box construction, a material that is structurally degradable in a known period of time before which the tree root system has alreadly been established at a depth which will not adversely affect adjacent paving or like structures.
A method of installation for root control planters is to pack the surrounding hole annulus with rock, whereby water percolates downwardly to the root system emanating below the planter box. The tree roots inherently seek moisture and nutrient, it being an object of this invention to provide nutrient application means in the planter structure, whereby nutrients can be directed to the roots where they emanate from below the planter box.
The square thin walled planter boxes of the prior art tend to be weak and deformable into paralleogram configuration, since the corners thereof are not reinforced. It is an object of this invention to provide a polygonal planter box form with reinforced corners, advantageously employing the aforesaid nutrient application means. It is also an object of this invention to modularize the planter box structure whereby one regular panel configuration suffices in a multiplicity thereof to produce the polygonal planter box assembly. Furthermore, the aforementioned nutrient application means is advantageously employed in combination with the multiplicity of panels to secure and reinforced the corner joinder of said panels.